The costs of staging a full-scale musical with professional singers and instrumentalists are prohibitive for all but a handful of large theaters in the area. For those audiences (and performers) who want more musicals than they’re getting, one alternative is a concert staging, in which the cast and orchestra perform the script and score of a show, while leaving the visual elements to the imagination. Concert stagings are fairly frequent in other cities, but not here: hoping to fill the gap, Marshall Productions is making its debut with a one-night-only concert version of A Little Night Music. With Richard Hoffman conducting a 19-piece orchestra, the performance will feature a cast of young but seasoned musical-theater actors, including Robert Heitzinger, Skipp Sudduth, Suzanne Petri, Linda Balgord, Leo Daignault, Elizabeth Muckley, and Judy Kaplan. Stephen Sondheim’s intoxicating, waltz-based score and Hugh Wheeler’s witty script should fare nicely in the hands of strong performers like these. Producer Thomas Marshall has previously put on concerts its in local cabarets, featuring music by the likes of Kurt Weill, Jerome Kern, and Cole Porter: this is his company’s first venture into a full-sized theatrical venue, and the results will bear watching. Civic Theatre, August 29 (20 N. Wacker, 915-0272). Tuesday, 8 PM. $18.50; reservations required.